Wednesday, May 25, 2011

When considering an organism within an ecosystem, the most important influences taken into account are above ground plant-plant interactions and animal-plant interactions and prevalent abiotic factors. However increasing evidence suggests that plant-microbial interactions in the rhizosphere play just as important a role. Take for example growth of the Hedge Woundwort, Stachys sylvatica. This unpleasant smelling perennial is generally found in hedgerows and forest verges, preferring humid soil and intermediate light (1). It can reproduce clonally by means of runners, and produces spikes of reddish-purple flowers from June to October.

Hedge Woundwort, Stachys sylvatica

In order to investigate the effect of different soil biota on S. sylvatica, plants were grown in artificial soil inoculated with soil the rhizospheres of two different locations: a hedgerow and a forest understory (2). The innocula were processed to remove soil fauna, leaving only the mycorrhizal ans microbial communities. Strikingly, the two different innocula produced two very different plant growth responses. The S. sylvatica plants grown in the presence of the hedgerow innoculum produced plants with a higher biomass and clonal runners than those with the forest verge innoculum. In addition, the forest verge innoculum plants showed a higher number of flower infloresences than the hedgerow innoculum plants. For S. sylvatica, this shows that soil biota drive possible adaptive growth strategies.

Tuesday, May 24, 2011

Misumena vatia is a common crab spider (Thomisidae), one of 14 species of crab spiders in Ireland (1). Resembling crabs in their appearance and in their movements sideways and backwards, the larger females can be found sitting on flowers, waiting to pounce on prey such as hoverflies and bees that feed on the flowers (2). M. vatia is most often seen on white or yellow flowers and quite amazingly the spider can change its colour, chameleon like, to camouflage to its background (3). Colour change occurs over a period of days and this ability is due to the presence of ommochromes in the spider, a group of pigments that are of widespread occurrence in insects and some other arthropods (4). There is some debate whether the ommochromes actually act primarily as a protection against photodestruction by intense UV light (4), but the fact that M. vatia possesses the physiological ability to distinguish between certain colours in its environment (5) lends credence to them playing a role in mimicry.

Monday, May 23, 2011

Very often I have come across species, of plant, animal and fungus, that upon searching the literature, reveal themselves to be actually a species complex, a number of species that are identical in many respects but are genetically distinct. The levels of these distinctions are often quite striking, as in the case of the Green Lacewing Chsysoperla carnea (Insecta: Neuroptera: Chrysopidae). This is a common insect of the summer months that is most recognisible from its almost ponderous flight and transparent, well veined wings. In the autumn time, the green adults hibernate, often indoors, their bodies turning a pinkish colour (1). The larvae feed on aphids and are used commercially to control aphid.

Chrysoperla carnea

C. carnea has been shown to be a complex of many cryptic species, based on the songs they make to attract mates (2). When sexually receptive, members of the C. carnea group vibrate their abdomens, which in turn causes the substrate (generally a leaf) on which it stands to vibrate, generating a song. This process is known as tremulation. Both sexes tremulate, so only individuals with the same songs will be attracted to each other, and since song is genetically determined, this results in reproductive isolation of populations charactrerised by song. At least 15 groups within the C. carnea group have been described, differentiated by song (3).

Chrysoperla carnea

As Neuropterans, lacewings are considered some of the oldest insects with complete metamorphosis (4). Ancient, extinct Neuropterans can be traced back to the Late Permian period, 260-251 million years ago. Of the current c. 6000 species of Neuropterans described, about 1200 belong to the family Chrysopidae, to which the C. carnea group belong.

The Dryad's Saddle mushroom (Polyporus squamosus) is a large, fleshy agaricomycete that grows in a semi-circular or saddle shaped fashion on a range of both living and dead broad-leaved trees, such as ash, elm, sycamore and beech (1). Its upper surface is creamy yellow in colour which is marked with concentric rings of brown scales. The under surface appears as a network of pale yellow, polygonal spores.

Underside of Dryad's Saddle, Polyporus squamosus

While P. squamosus is edible, it needs to be picked young as the older mushroom is quite tough and corky. However, if processed, the resultant biomass may present a viable animal, and possible human, source of nutrition (2). In addition, P. squamosus produces pectinases (3), enzymes that degrade pectin and that are used in the fruit industry to improve juice extraction from apples, etc. (4). A polymer-polymer two phase system has been successfully used to produce both P. squamosus biomass and resultant secondary metabolites (5). This method consists of two mutually incompatible structural polymers (namely polyethylene glycol and crude dextran) in solution which brings about a spontaneous separation of phases. This reduces the need for mechanical separation of cells. P. squamosus fungal growth is restricted to the bottom phase, leaving the top phase free.

Dryad's Saddle, Polyporus squamosus

P. squamosus has also been shown to produce useful xylanase (6) as well as a lectin that shows great potential for usein glycobiological studies in biomedical and cancer research (7), making this method of growth a useful biotechnological tool.

Friday, May 20, 2011

Tenthredo livida is a common sawfly of holartic distribution that is often found in hedgerows and woodlands. The female lays eggs into plant tissue, using saw-like ovipositor to make the inscision. Larvae are polyphagus, feeding on a variety of plats such as hazel, willow and even bracken. The adults will hunt flies and take nectar from plants (1).

Tenthredo livida

Interestingly, calling T. livida a sawfly, or "Symphyta", is now considered incorrect. The Symphyta are a basal grade that leads to the long waisted hymenoptera. Therefore Symphyta is not a monophyletic group, that is within the group not all relatives are included (2). The terms "Symphyta" and saw fly are still used however, in an informal way.References:

Wednesday, May 18, 2011

While I have previously written on this blog that scale insects tend to be quite small, a large example has recently come to my attention. Pulvinaria regalis, or the Horse Chestnut Scale, is c. 6 mm in diameter, and the female is particularly visible this time of year when they produce a large, white, fluffy, ovisac into which up to 2,000 eggs are layed (1). Upon laying the eggs, the female dies, but remains attached to the ovisac as a protective shield. Without the ovisac, Pulvinaria regalis is excellently camouflaged against the bark of its hosts, Horse Chestnut, Linden and Elm species (its many hosts making it polyphagus), where it feeds by extraction of sap. Once the young hatch, they are easily dispersed by the wind due to their small size (2)

Horse Chestnut Scale, Pulvinaria regalis

P. regalis is thought to be of asian origin, and was first recorded in Europe in 1968 (2). The first record for Ireland was as recent as 2000 on a horse chestnut tree in Dublin, and the authors speculated then that P. regalis may spread throughout the country (3). This has proved to be the case as shown by this sighting in Cork city.

Horse Chestnut Scale, Pulvinaria regalis on Linden Tree

P. regalis is a particularly urban insect in Ireland, and Britain, where its host plants are not native (2). It rarely causes significant damage to trees, proving to be just rather unsightly.

Saint Patrick and Shamrock go hand in hand, like bread and butter or Laurel and Hardy. Legend has it that the saint used the three leaved Shamrock to demonstrate the Christian holy trinity, how the father, son and holy spirit could exist as one. Yet, while Saint Patrick makes numerous references to the trinity in his writings, nowhere does he mention the Shamrock (1). The association came some time after his death, most likely the co-opting of a pagan symbol into Christianity. Indeed the identity of the Shamrock is hazy to say the least, with various sources identifying it as wood sorrel, white clover and black meddick (2,3).

Flowers of Saint Patrick's Cabbage, Saxifraga spathularis

However, there is another plant that honours Ireland's patron saint, one much more deserving of the role. Saint Patrick's Cabbage is a saxifrage that bears the saints name both in its common name and its binomial moniker, Saxifraga spathularis. It is a distinctly Irish plant, being found only on the Island of Ireland as well as northwestern Spain and the mountains of north Portugal (4), where it is commonly called abelairiña. Its clusters of green leaves bear stalked pannicles of pretty white flowers that show numerous pink dots on the petals. S. spathularis has a wide tolerance to soil conditions and can be found in a variety of habitats, from exposed mountains to the shade of humid woodlands. In Ireland, it is distributed along the west coast, from Cork to Donegal, however its main base is in Kerry and West Cork. Records have been reported from Tipperary, Waterford and Wicklow, but pressure on hedge banks could be reducing its incidence (4).

Saint Patrick's Cabbage, Saxifraga spathularis

S. spathularis is closely related to another saxifrage species particular to Ireland and northern Iberia, Kidney Saxifrage (S. hirsuta). The two species can in fact hybridise to form S. x polita, which is commonly found growing in gardens as False Londonpride. Areas where S. spathularis and S. hirsuta grow in close proximity have seen an increase in the hybrid to the detriment of the populations of these two species (5).

References:

Edna Barth, 2001. Shamrocks, Harps, and Shillelaghs: The Story of the St. Patrick's Day Symbols pp. 146-149

Colgan, 1892. The Irish Naturalist 1 pp. 95-97

Frazer, 1894. The Journal of the Royal Society of Antiquaries of Ireland 4 pp. 132-135

Monday, May 16, 2011

Of the four species of grebe regularly found in Ireland, the Little Grebe (Tachybaptus ruficollis) is the smallest. Little Grebes are found throughout the world, with the European population numbering > 99,000 breeding pairs, of which 1,000-2,500 are found in Ireland (1). A brownish bird, with chestnut cheeks and a lime green spot at the base of the bill in the breeding season (2), they nest in shallow waters of ponds, canals and slow moving rivers. This propensity for shallow waters is due to their feeding habits. As divers, the longer they spend under water, the longer their recovery time (3). This makes smaller water columns more attractive to them as they feed on a variety of arthropods, molluscs and even small fish and tadpoles. Study of the Little Grebe is often problematic due to its secretive nature (4), however it is known that harsh winters affect populations due to reduced feeding oppertunitites when open water sources freeze.

Little Grebe, Tachybaptus ruficollis

The grebes as a family (Podicipedidae) are the only members of the order Podicipediformes, and at first glance these small, diving birds bare little resemblance to the tall, filter feeding flamingo family, Phoenicopteridae. Yet recent analysis of mitochondrial and nuclear DNA from both families (5), as well as cladistic analysis of morphological characteristics (6) showed that the two are sister clades. This points to flamingos evolving, not from a shore like ancestor, but from a highly aquatic one. It also interestingly shows the evolution of two very different feeding strategies (foot propelled diving versus filter feeding) in birds.

Thursday, May 5, 2011

I tend to accumulate pictures of plants and animals unfamiliar to me for identification at a later stage. Some are easy, some hard and some are downright impossible to pin down. Take the little guy above. I knew it was a moth, just about, and a bit of research gave me an idea it was a member of the Cosmopterigidae. Further mining of databases reveled this Cosmet moth to be Chrysoclista linneella (1), The Linden Bark Borer (or, more appealing still, Linaeus' Spangle Wing). A great thank you is due to Angus Tyner of the MothsIreland Project for confirmation of this identity.

Linden Bark Borer, Chrysoclista linneella

However, once had found an identity, the reason it had been so hard to figure out became apparent: C. linneella has never been recorded in the Republic of Ireland (2). It may be even unrecorded in the whole island of Ireland as only one record exists, from Hollwood in Co. Down from 1855 and this is considered doubtful (3).

Linden Bark Borer, Chrysoclista linneella

C. linneella has a holarctic distribution, being found in most of Europe, Scandinavia, Russia and Britain, as well as North America where it was first reported as an introduction in 1928 (4). The c. 11 mm adults have metallic blotches against a vibrant orange wing and are visible from May to September (1). The larvae feed under the back of linden trees (Tilia spp.) and can cause considerable damage to plantations (4).

The specimen pictured was spotted on the bark of a linden tree in July 2010 in an area close to a large container port. This may have been a point of access for the moth.

Wednesday, May 4, 2011

The dark winged fungus gnats (Sciaridae) are a large family of flies (c. 1,700 species worldwide (1)), with 104 species alone described in Ireland (2). They are commonly found in moist environments, and some the larvae of some species are pests of commercial mushroom farms, specifically Lycoriella mali (3).

Sciara hemerobioides

Normally these 1 – 11 mm long flies are quite drab in appearance, with black bodies and appendages and dark wings (as the common name suggests). However one species that bucks the trend is Sciara hemerobioides. While its head, thorax, legs and wings are dark like other Sciaridae, it has a bright yellow abdomen with bold black strips across it. The adults can be seen in a variety of damp habitats, such as heathlands and wetlands, where the adults feed on nectar from umbelliferous flowers (4). The larvae feed on fungi and rotting vegetation.

Tuesday, May 3, 2011

Known to many as a coastal plant in Ireland, Common Kidney Vetch (or Lady's Fingers, Anthyllis vulneraria) is also an important constituent of calcareous grasslands, and it is in this guise that is most common throughout Europe (1). This perennial grows to 40 cm high but tens to a prostrate habit. The pinnate leaves are covered in small hairs, as is the stem and it has densely arranged, yellow to orange flowers (2). The flowers bloom for about 8 days (3), during which time some of the main pollinators are the Long Tongued Bee (Anthophora acervorum) and the bumble bees Bombus terrestris and B. jonellus. Both B. terrestris and B. jonellus are primary nectar robbers, in that they bypass restrictions imposed by flower structures to “rob” nectar (3). This often has deliterious effects on plants, but in the case of A. vulneraria such activity actually results in an increase in fruit production. The structure and arrangements of its flowers means that the bodies of the robbers brushes off the flowers, effecting pollination. Flowers open from the bottom to the top, and interestingly the resultant fruit and seeds are significantly heavier on the bottom compared to those further up (4). A. vulneraria is also the only larval food plant of the butterfly Cupido minimus, and unfortunatley both plant and butterfly are considered endangered in Lower Saxony, Germany (5).

Common Kidney Vetch, Anthyllis vulneraria

A. vulneraria has been recently used to show the effects of fragmentation on populations (1). Fragmentation is the overall reduction and breaking up of an organisms habitat, which itself results in population fragmentation for that organism. While fragmentation is thought to be a cause of speciation (6), populations exposed to it then become vulnerable to extinction (7). A study of populations of A. vulneraria in calcareous grassland exposed to significant fragmentation however, revealed little genetic differentiation between fragment populations. This was due to the nature of the use of the grassland as pasture for sheep. As the sheep move from fragment to fragment, they bring with them on their coats, on their feet and in their dung seeds of A. vulneraria from other locations. These new arrivals help keep a diversity of genetic stock in A. vulneraria populations, reducing any inbreeding depression. This indicates that sustainable management of grazing will help to maintain species diversity in grassland pasture.

Monday, May 2, 2011

With its narrow waist and yellow and black striped colouration, one would be forgiven for assuming Conops quadrifasciatus was a solitary wasp. Closer inspection however reveals one set of wings, as opposed to hymnopterans' two sets, which places it firmly with the dipterans. C. quadrifasciatus is one of a number of similar conopid flies that are present in Europe (1), with 11 species of the family present in Ireland (2). Adults feed on a variety of flowers, including ragwort (Senicio jacobaea) as seen in the pictures.

Conops quadrifasciatus

However, any affinity conopid flies have with hymnopterans is entirely superficial as they are major parasites of bumblebees. The adult female fly attacks foraging worker, male and queen bumblebees outside the nest, placing eggs onto or in the abdomen of the host. The larva hatches and resides in the abdomen of the bee, feeding off haemolymph and the bee's internal organs (3). The bee dies during the last larval stage and pupation takes place inside the body of the bee.References:

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